Adaptive Virtual Game Worlds: Where to Begin?

Brian Lacy · 2004-04-19T09:16:33

I have several questions for the experts in this forum, which I''ll get to in a minute. First some background... For years I''ve been fascinated with the idea of developing a game involving a persistent virtual world whose makeup and events evolve through the actions of NPCs. Individual and Group relationships, motivations, and beliefs, all facilitate the process. Utlimately the player is placed within the virtual world, the state of which is dynamically defined (at least in part) by the behavior of the NPCs. A story develops -- it is not "generated" but simply occurs based on the behavior of all the agents working together. I''d like to summarize a scenario I wrote that kind of explains what I mean. It''s based in a virtual world with a traditional fantasy setting, and focuses on a small geographical area containing one village and a system of nearby caves. Consider that the world contains a male, human NPC (let''s call him John). John is one of roughly fifty NPCs that live active, believable lives in the village. Some are farmers, others are merchants, authority figures, etc. John, however, is none of these things. The pre-generation of John''s character defined him as greedy, lazy, opportunistic, sneaky, and cowardly, yet charismatic. With these tendencies, John has a habit of sneaking into other villagers'' houses to relieve them of their more precious belongings -- whatever John believes will be most valuable. Suspicion mounts among the other NPCs that John is the culprit. As the belief that John is guilty is shared among them, a group belief evolves that John must be confronted and, if he''s guilty, punished. John, fearing what may be done to him, packs up his relocated goods and moves off in the middle of the night to one of the nearby caves. It turns out that John has amassed a small but loyal group of pretty tough friends among the NPC villagers. These friends join him at the cave and vow to protect him. Enter the player. The NPC villagers are quite miffed about the whole event and would like to get even, but John has disappeared. The common belief is that John is hiding in the caves (i.e., since there''s no where else to go), but those who have sought him there have not returned, and rumors abound that John has hired superhuman thugs or even evil outerworldly beings to protect him. They want their stuff back, and they are especially interested in getting even, so they''re willing to offer a hefty reward to anyone who will confront John and return with their belongings. The player of course has a quest laid before him, with a decent challenge and reward. But the quest was 100% dynamic -- its existence is owed entirely to the behaviors of an NPC with a certain random grouping of characteristics and a specific set of environmental factors. So that''s the scenario.. it''s extreme and complex, and hardly perfect, but it illustrates the general concept. There are several things I''d like to know from all you experts. First, I''d like to be able to be able to use the proper terminologies to define the idea. Second, I''d like to understand what aspects of AI are most applicable -- does fuzzy logic come into play? Where, when, and why? Is the concept of neural networks applicable here? At what level -- the individual level? The group level? Third, has any research been done in this specific[/ia] area? Where can I go to find people who are interested in exploring similar ideas? Has anything remotely like this (even on a far simpler level) been attempted? As a final note, I want to make sure everyone understands that I''m not naive about this -- I realize it''s pretty far out there in terms of what is possible, let alone feasible, with today''s AI technologies. Even if it were practical for the right team, I expect it would take years to develop. I just need to start establishing some solid basic understanding of the concepts of AI as they relate to my particular application of interest. All input is appreciated. Thanks. **************************************** Brian Lacy ForeverDream Studios Comments? Questions? Curious? brian@foreverdreamstudios.com "I create. Therefore I am."

Artificial Intelligence Programming

Started by irbrian March 18, 2004 01:20 AM

89 comments, last by irbrian 20 years ago

irbrian

130

Author

April 02, 2004 04:35 AM

quote:Original post by Timkin
I'm curious as to the reference for this information. I work in the neurosciences and this doesn't sound like any accepted theory to me. It does, however, sound like a computer science view of neuronal networks from the 80s. Perhaps it's just because you've paraphrased it though, that it reads that way. If you have a specific reference, I'd be very interested to read it.

It's likely I'm misreading here, but your implication seems to be that I'm making this stuff up. Well, I don't remember the precise moment at which I claimed to be an expert on neuroscience.

What I wrote above was not merely paraphrase, it was a paraphrasing of my interpretation of various things I've read and heard over many years, and I couldn't begin to vouch for the accuracy of any of it, let alone the specific sources. Apparently I'm pretty far off.

quote:There are competing theories for how memories are stored, at least from the literature I've read. One is that memories are stored by little folicles on certain cell bodies and these follicles affect the firing behaviour of the neuron under external stimulus. Another view is that memories are stored in synaptic sensitivity to inputs. The problem with this model is that it doesn't explain how one part of the brain (the same neuronal columns for example) can store multiple memories (since they don't really store multiple synaptic sensitivies. Certainly, research into the olfactory system (which has been completed understood now for many years) tells us that smell memories are encoded in a manner that generates lower dimensional, stable attractors in the signal phase space. That is, the unstimulated state of neuronal loops in the olfactory system is a chaotic attractor. When these loops receive stimulus, the dynamics collapse to a simpler, stable, periodic or quasi-periodic behaviour, signalling a change in the attractor of the system. Unfortunately this model doesn't extend to all regions of the brain. For example, in the occipital lobes of cats, it has been shown that some information is actually encoded in the varying phase synchronisation of discrete neuronal columns (spatially distinct neuronal loops). Recent work on rat hippocampi has supported this view of information encoding. How this relates to memory though is not known at this time.

Sounds much to complicated to try go about modeling it for any game.. maybe even for any AI simulation. Frankly, however inaccurate, I like my original interpretation better.

quote:On the significance issue... I think that there are really two levels of significance of information: significance to us and our perception of significance to others. Significance to us is, I think, best measured by the emotional response that the information generates. Significance to others could be measured by how many other people mention the information to us, or ask us about it, or alternatively, how other people (and how many) responded to the information (emotionally speaking). Bill telling Mary that he finds the information significant should be different to Bill telling Mary that the whole town was in an uproar when they heard the information. This might even affect the significance of the information in Mary, depending on her empathy for others and her 'community spirit'.

I think this goes back to NPC Observation and forming of Belief relevant to the character's observation. Between the nature of the observation and the significance of the actual information to the character receiving the information, a new level of significance might be established.

[edited by - irbrian on April 2, 2004 5:35:45 AM]

---------------------------Brian Lacy"I create. Therefore I am."

Timkin

864

April 02, 2004 05:52 AM

quote:Original post by irbrian
It''s likely I''m misreading here, but your implication seems to be that I''m making this stuff up.

That''s certainly NOT what I''m saying. I was asking because in all likelihood you were talking about a model that I had not read about, or that I had read about, but that which I could not identify from what you wrote. Since it''s important in my job for me to keep up with current theory and practice, I asked for a reference. Nothing else was meant by that.

Timkin

Thesolitas

122

April 02, 2004 12:29 PM

quote:Applying this to the general idea of NPC memory recollection, NPCs would always keep their memories, but the less significant the memory and the less frequently the memory is accessed, the more the memory fades. Maybe the system could institute a formula that determines how significant a memory must be to be recalled efficiently after X amount of time, weighted differently for different NPCs? i.e. Significance Threshold Over Time...

On the topic of memory recall, I think we''re going about it wrong. Memories should be stored in a LIFO structure, last in, first out. As you add memories, it pushes older memories to the back. Whenever you do something that needs to check memory, you start looking through memories from the front. Depending on how long you allocate to that process, determines how far back in memory you go. How far back you can go can change, since sometimes, we just try harder to remember something. Everytime you access a memory succesfully, you could bring it back to the front. So memories that you use constantly, are always staying near the front.

Now how do you add significance to that? One thing I was thinking, is that as you add memories, you take the significance of that new memory, and push it down the list till it finds either an equal, or lower significant memory. This way, higher significant memories don''t get pushed down.

How exactly do we determine significance though? Their are alot of different methods being thrown around, including emotional response to the memory, number of times they''ve heard a memory, number of people that have told them, etc.

Number of times heard/number of poeple heard from should really only keep that memory to the front longer. The emotional response to that memory should make it more significant. You can be told 20 times the same thing, and though it may stay to the front for a while (because of constantly being told), if you don''t care, you''ll forget it.

If you''re at a party, and 2 women tell you their phone numbers, one you like, one you don''t, who''s number are you going to remember?

The problem is, how do we determine the emotional significance? And what about memories tied to an emotional response that change? How do we decay the significance of a memory?

ironfroggy

122

April 03, 2004 06:36 PM

I really want this to move completely to the group, to make it easier to track, so im double-posting. sorry to the few of you who are in the group yet.

In response to all the talk about the recalling and memory significance. I think we need two values for that, simply. They would be SigniAlpha and SigniBeta, both between 0.0 and 1.0.

In a newly created memory, SigniAlpha would be nearly 1.0 and SigniBeta would be nearly 0.0. Anytime a memory is accessed, both are raised, but SigniAlpha much more than SigniBeta. Over time, both values drop, but SigniAlpha more quickly than SigniBeta. When SigniBeta drops to 0, the memory is forgotten. Perhaps, there could also be a threshold for SigniBeta to reach where it will never drop below again (moving from short-term to long-term memory).

The recallability of a memory would be a product of SigniAlpha and SigniBeta, weighted mostly for SigniAlpha.

This would cause new memories to be forgotten quickly if they aren''t thought about (apparently not important) as they wouldnt be accessed enough to keep SigniBeta above 0. After that value is raised however, SigniAlpha can drop low enough to make the memory difficult to recall, yet the memory is still retained because of the value of SigniBeta.

I''ve been doing lots of my own work on the subject, mostly research and hypothosis and this is one of the things I''ve been working with. I''m trying to mention my ideas carefully tho, as I need to make sure they aren''t brain-dead, first :-) I''m also doing some demos of the ideas, which I''ll post on the group.

(http://www.ironfroggy.com/)(http://www.ironfroggy.com/pinch)

Timkin

864

April 04, 2004 09:02 AM

I can in no way support the move of this thread to a Yahoo group that is unrelated to GameDev. The contributions made in this thread belong here. Anyone is, of course, free to post wherever they like. Personally I''m not going to join a Yahoo group for the discussion of Game AI when I can do that here. Splintering into disassociated groups will, IMHO, only do damage to GameDev by removing important and interesting discussion from these forums.

Cheers,

Timkin

Jotaf

280

April 04, 2004 11:32 AM

I agree with Timkin, if you''re gonna do that, make it possible for someone who is not registered to at least read the discussions... the fact that registration is required just to have a look at them is very annoying.

Anyways, great discussion =) lots of good ideas. I''d like to make a suggestion though. I found a nice way to model knowledge in a game, it''s easy and very flexible. I described it in this thread, I''ve got 4 versions of it, the first 2 are enough for almost anything you can think of and VERY lightweight for a game with thousands of NPCs, you can find them in that thread; I also have another one that I''m still working on a prototype (it''s done but I''m having trouble coding an editor that is intuitive enough =) ), and the 4th I believe should be able to model knowledge just like it is stored on the human brain (it''s consistent with all the studies I read about), but it''s a bit too complex for a game. Ok here''s the thread, you probably already checked it out but I thought it would be worth mentioning:

http://www.gamedev.net/community/forums/topic.asp?topic_id=211811

ironfroggy

122

April 04, 2004 01:16 PM

I understand the desire to keep the discussion at gamedev. and, dont get me wrong, i love gamedev. But a single forum thread is not a very good enviroment for an on-going discussion like this, especially if any projects come out of it. the idea of the yahoo group is to create an eviroment that can support something lasting so long.

Maybe if gamedev had hierarchial forum threads and an option to be mailed the threads, it would be different. I, for one, prefer my email client to coming back here every day and trying to see what the last message was that I read and which ones are new and who is replying to what messages, etc.

I''ll continue to double post (aside from this, no need obviously) until this thread dies down considerably as it inevitably will. I do agree the group archive should be public, i think the members-only setting was just a default.

(http://www.ironfroggy.com/)(http://www.ironfroggy.com/pinch)

irbrian

130

Author

April 04, 2004 08:45 PM

Truthfully, the idea of implementing NPC memory in any type of linear fashion deeply bothers me. Humans don't think in a linear fashion, and while I realize that we're not talking about making artificial Humans here but game characters, I don't see how one can operate a truly convincing AI NPC without at least paying attention to how humans' minds operate on an abstract level.

I have relatively insignificant memories from as far back as my 3rd Christmas. Yet there are significant events I don't remember too well, if at all -- although those memories might resurface if I thought about it enough and had some help (like talking to family members about them).

I think NPCs should, at least in a general sense, have the same capability. It makes sense of course for more significant memories (i.e. my wife died) to be more easily accessible for longer periods than insignificant ones, but certainly any memory should be accessible to some degree given enough stimulation.

[Off Topic]
Regarding the Yahoo! group, I had a heck of a time trying to get access and I STILL haven't successfully been able to access the discussions there. Furthermore, I've always hated anything Yahoo! related for half a dozen reasons unrelated to this.

On the other hand, while I understand Timkin's position, I do think the topic would be best discussed in a more dynamic format. I'm all for a group of some kind, but I've officially and resolutely dismissed Yahoo! as the solution.

Oh, and I never really liked the tree-oriented post/reply structure. So between that and my general distaste for Yahoo, I think I'll keep talking about it here until someone comes with a better proposal.
[/Off Topic]

****************************************

Brian Lacy
ForeverDream Studios

Comments? Questions? Curious?

"I create. Therefore I am."

[edited by - irbrian on April 4, 2004 9:47:08 PM]

---------------------------Brian Lacy"I create. Therefore I am."

ironfroggy

122

April 04, 2004 09:39 PM

Yeah, I''m sure you could remember your third christmas if you talked about it with family members. I''m also sure you''d be very wrong about most the events. They probably would be, too.

I''m surprised this issue hasn''t been raised before. What about remembering things incorrectly? When you have trouble remembering an old memory, as much as you remember more details you just fill it in with things that seem right.

Should this be implemented in the kind of systems we have been discussing?

(http://www.ironfroggy.com/)(http://www.ironfroggy.com/pinch)

irbrian

130

Author

April 04, 2004 10:54 PM

Good point! Definitely an intriguing aspect to consider. I did actually think about this at one point. I wonder if it could be implemented naturally as a side effect of other concepts we''ve discussed, though. I.E., when an NPC stores a memory, he technically stores it in small chunks, and some of those chunks may be recalled more easily than others. If a chunk seems to be missing as the NPC Agent isn''t able to recall the complete memory, the NPC either conveys the incomplete information as is, or treats the memory as an observation and tries to piece together what might have happened. Maybe the resulting belief will be correct, maybe not. Over time, these beliefs may even begin to replace the original beliefs, thus causing different NPCs to recall events with subtle variations.

So, it comes down to an NPC being able to take given information about which it has already made an observation or formed a belief, compare the data, and potentially draw additional conclusions.

Guess I''m talking pretty advanced stuff here -- NPCs drawing natural, logical conclusions off of incomplete information, including info drawn from their own "memories" -- but it would be cool, no?

****************************************

Brian Lacy
ForeverDream Studios

Comments? Questions? Curious?

"I create. Therefore I am."

---------------------------Brian Lacy"I create. Therefore I am."

Adaptive Virtual Game Worlds: Where to Begin?

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Adaptive Virtual Game Worlds: Where to Begin?

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